Fatigue Strength Verification of Stiffener-Frame Connections - DNV Class Notation PLUS

摘要

The DNV class notation PLUS offers an extended scope of fatigue strength verification for hull structural details. The objective of the PLUS notation is to document the fatigue life of critical areas in the vessel. This paper presents the scope of the PLUS notation together with a summary of the revised calculation procedure for longitudinal stiffener to web frame connections, and the background for revising the class notation. The new calculation procedure uses a 50x50mm mesh finite element model of the stiffener to web frame connections, together with stress concentration factors to obtain hotspot stress for fatigue analysis at critical locations. This enables efficient fatigue analysis of all longitudinal stiffener connections. The 50x50mm model captures local stress patterns around cut-outs, knuckles, web frame toes and tripping brackets and gives also an accurate shear stress distribution from the longitudinal to the web frame. The relatively detailed stress distribution makes it easy to distinguish between the critical and not critical connections.